松材线虫侵染不同抗性松树后寄生适应性与致病力的变化

Changes in the Parasitic Adaptability and Pathogenicity of Bursaphelenchus xylophilus After Infection on Pine Trees with Different Resistances

为研究不同毒力松材线虫在不断侵染抗性不同松树后其寄生适应性和致病力的变化,选取松材线虫强毒和弱毒虫株,循环接种至不同抗性松幼树(抗性马尾松、火炬松和黑松),通过测定松材线虫致病力、种群相关寄生适应性(RHS)系数、种群性比及线虫分泌的纤维素酶活的变化,探究松材线虫寄生适应性与致病力的变化规律。结果表明:不同抗性松幼树无论是接种强毒还是弱毒虫株,其感病程度高低顺序依次为黑松>火炬松>抗性马尾松;经循环接种线虫3次后,3种松幼树的发病率均提高;且无论是强毒还是弱毒松材线虫种群其RHS系数均明显提高循环侵染抗性寄主后松材线虫多数种群的雌雄性比增加。通过检测松材线虫种群纤维素酶活力的变化表明,循环接种不同抗性寄主均不同程度地增加了松材线虫种群的纤维素酶活力,且循环侵染高抗马尾松幼树的增强效应最为显著。将经循环接种后的松材线虫虫株再接种黑松幼树进行致病力测定发现,接种经循环接种处理的强毒和弱毒松材线虫虫株的黑松幼树其发病时间较对照均不同程度缩短,其中发病最快的为接种ZJ-Ma种群和ZJ-Huo种群;即便发病最慢的接种YW4-Huo种群和YW4-Hei种群的处理也比对照提前12 d发病;且接种YW4-Ma、YW4-Huo和YW4-Hei种群的黑松的发病率分别达到87.5%,87.5%和75%。因此松材线虫通过多次侵染松幼树其种群适应性可得到明显提高,雌虫比例会增大,致病力会进一步增强,且循环侵染抗性松幼树后的增强效应更为显著。

To study the changes of parasitic adaptability and pathogenicity of Bursaphelenchus xylophilus with different virulence after cyclic infection on pine trees with different resistances. We selected high virulent strain ZJ and low virulent strain YW4 of B. xylophilus and inoculate them into different resistant pine seedlings(resistant Pinus massoniana, P. taeda, and P. thunbergii). By measuring the pathogenicity, relative host suitability(RHS) coefficient, population sex ratio, and cellulase activity of B. xylophilus, the changes in parasite adaptability and pathogenicity of B. xylophilus were explored. The results showed that the susceptibility of different resistant pine seedlings, whether inoculated with high virulent strain ZJ or low virulent strain YW4, was in order of P. thunbergii > P. taeda > resistant P. massoniana. After 3 cycles of inoculation with nematodes, the incidence of the 3 pine seedlings increased;the RHS coefficients of both the high virulent and low virulent B. xylophilus populations were significantly increased. The female-to-male ratio of most populations of B. xylophilus increased after cyclic infection of resistant hosts. The detection of changes in cellulase activity of the B. xylophilus populations showed that the cycle inoculation of different resistant hosts increased the cellulase activity of B. xylophilus populations to varying degrees, and the enhancement effect of circulating infection with high resistance P.massoniana seedlings was the most significant. The B. xylophilus strains after circulating inoculation were re-inoculated into P. thunbergii seedlings for pathogenicity determination. It was found that the incidence time of P.thunbergii seedlings inoculated with the high virulent and low virulent B. xylophilus populations was shorter than that of the controls. The pine seedlings inoculated with the ZJ-Ma and ZJ-Huo populations had the fastest incidence, and the pine seedlings inoculated with the YW4-Huo and YW4-Hei populations had the slowest incidence,but they still occurred 12 days earlier than the control. Also, the incidence of pine seedlings inoculated with YW4-Ma, YW4-Huo, and YW4-Hei populations was as high as 87.5%, 87.5%, and 75%, respectively. These results indicated that B. xylophilus can increase the population adaptability, proportion of female and pathogenicity by infecting pine seedlings multiple times, and the enhancement effect when circulating infesting resistant pine seedlings is more significant.